1. Technical Field
The invention concerns improved trick mode playback, and more particularly to improvements in trick mode playback of digital audio content at other than normal speed.
2. Description of the Related Art
Trick mode playback from a DVD can include speedup or slowdown from normal play speed to either search for a specific location on the disc or to look at details of a clip that would be missed at normal speed playback. By convention, normal playback speed can be denoted as 1X. Both audio and video trick modes are possible and both can be found on commercially available DVD players. However, conventional methods for playback of audio at fast or slow speed have proved to be problematic. The advancement of digital signal processors and especially audio digital signal processors that are used in currently available products have created the possibility for more sophisticated real-time processing for improved audio trick modes.
One problem with the use of video trick modes concerns the treatment of audio corresponding to a playback video segment. For example, when a user speeds up or slows down a displayed video segment, the corresponding audio segment that is played back can be distorted. Typically, audio samples in the audio segment can be shifted to higher frequencies during a fast trick mode, and lower frequencies during a slow trick mode. The fast trick modes that increase the playback speed by a factor of between about 1.5 to 3 times as compared to normal playback will tend to cause human speech to sound higher in pitch. This higher pitched audio playback, the chipmunk effect, can be annoying and in many instances may be unintelligible for a listener. Conversely, slow frequency trick modes can produce a low frequency wobble that may be understandable but not aurally pleasing.
In order to obtain the most useful audio playback during video trick modes as described herein, it can also be necessary to consider the nature of the particular trick mode. For example, while it may be possible to utilize various techniques to provide intelligible audio for at a particular trick mode speed, for example 1.5X, such techniques may provide unsatisfactory results at much higher trick mode speeds, for example 6X or 10X. At such high playback speeds, any attempt to play audio content in synchronism with, or at least at a corresponding rate to that of the video programming may result in unintelligible speech due to the rapid rate at which words would need to be delivered.
To avoid hearing various types of audio artifacts that can be produced during trick mode playback, conventional DVD players will often mute the audio during video trick modes. However, this is not an entirely satisfactory solution as the audio may be of interest in such modes. Accordingly, it would be advantageous if a DVD player could playback audio in a manner that overcomes the limitations of the prior art and achieve a desirable and aurally pleasant playback of audio during video trick modes.